Scaffolding generally comprises vertical supports or frame members, bracing or connecting members, and connection and retention devices for temporarily securing together the members to form the desired scaffolding at the job site. The connection and retention device may be mounted to either the vertical support or the bracing member, and the other member may be altered to cooperate with the connection and retention device to secure the members together.
The design of scaffolding, and particularly the design and function of the device utilized for securing together the vertical members and bracing members, presents two frequently conflicting objectives: (1) the design must be safe, not only structurally, but also from the standpoint of minimizing or eliminating operator error in erecting the scaffolding, and (2) the design should be easy for the operator to utilize, thereby not substantially increasing the time or effort required to erect or disassemble the scaffolding.
Various types of scaffolding connectors or joints have obviously been devised, including the wedged-clamp joint described in U.S. Pat. No. 4,140,414, and the transom and spigot construction shown in U.S. Pat. No. 3,179,212. Probably the most popular type of scaffolding connectors employ a stud which generally is welded to and projects from the vertical support, with the bracing supports provided with an aperture for sliding over the stud. U.S. Pat. No. 2,701,167 illustrates such a design, which includes a gravity-responsive latch or dog to temporarily lock the bracing support to the vertical support. U.S. Pat. No. 2,810,612 discloses a hollow stud and an elongated latch pin, and U.S. Pat. No. 2,847,259 discloses a hollow stud with a leaf spring inside the stud biasing the dog in the downward direction. In U.S. Pat. No. 4,188,143, a pivotal member is similarly biased by a leaf spring in the upward position. The background of scaffolding art and particularly devices for temporarily securing together scaffolding members is discussed in these references, Which are each hereby incorporated by reference in their entirety into this application.
One need not be skilled in the scaffolding art to recognize the serious consequences of a scaffolding collapse or failure. Moreover, scaffolding is frequently erected and disassembled by relatively unskilled and inexperienced personnel. Also, scaffolding is frequently used in an environment that favors the accumulation of debris on scaffolding members which further increases the need for a reliable, easily utilized, and most importantly, a safe scaffolding retention device and method. One of the problems with some prior art scaffolding connections, such as that shown in U.S. Pat. No. 4,140,414, is that the connection devices are relatively expensive to manufacture and may be unintentionally misused by personnel erecting scaffolding.
The collapse or failure of scaffolding frequently occurs because the connection between the vertical scaffolding members and the bracing members has not been properly made. Moreover, such an improper connection is generally not easily observed by either the personnel erecting the scaffolding or the personnel utilizing the scaffolding. Thus, a problem exists with the prior art scaffolding in that an improper connection between support members and cross members may be sufficient to temporarily support the scaffolding and personnel, but vibration or other change in conditions suddenly results in the dislodgement of connected members and the collapse of the scaffolding. If, for instance, one of the dog members shown in U.S. Pat. No. 2,701,167 did not easily rotate relative to the stud and were to "freeze" in the up position after the bracing latch had been placed on the stud, the operator erecting the scaffolding may erroneously believe a proper connection had been made. The bracing member may thus be supported by the stud, but since the dog had not fallen properly in place to lock the bracing member to the stud on the vertical member, the bracing member thereafter may vibrate off the stud causing the collapse of the scaffolding. Similarly, the leaf spring shown in U.S. Pat. No. 2,847,259 could break or the dog jam within the hollow stud so as to hold the dog in the horizontal position, and an operator probably would not know that the leaf spring had broken.
The disadvantages of the prior art are overcome by the present invention, and improved apparatus and methods are hereinafter provided for temporarily securing together scaffolding members.